How do I answer a civil complaint foreclosure in Wisconsin working with a third party?

We need more details. Who is the third party? Are you being foreclosed on? What is your defense? A foreclousre occurs when you haven't paid your mortgage so how far in arrears are you?

I am not sure what you mean by "working with a third party". Do you mean that you have found someone who wants to buy the property? If so, it is generally a good idea to work with the lender bank (or loan servicer), lender's attorney, and other interested parties as soon as possible, to negotiate a deed in lieu of foreclosure or other such settlement. You should definitely at least consult with an attorney experienced in mortgage foreclosures.